It is well known that aircraft brakes typically employ a stack of alternatingly interleaved stator and rotor disks, such disks being adapted for selective frictional engagement with each other. The stator disks are typically splined to the axle of the aircraft, while the rotors are keyed to the wheel. As is known in the art, a series of beam keys are circumferentially spaced about an inner portion of the wheel and engage key slots in the outer circumferential surface of the rotors. The beam keys typically have one end thereof pinned to the wheel, and an opposite end mounted to an outrigger flange of the wheel. As shown in FIG. 1, a beam key and wheel assembly in accordance with the prior art is designated by the numeral 10. Here, a beam key 12 is mounted upon a foot 14 which in turn is engaged to an outrigger flange 16 of the wheel 18. A nut and bolt assembly 20 attains the secured engagement of the beam key 12, foot 14, and outrigger flange 16. The bolt of the nut and bolt assembly 10 is a shear bolt. Typically, a thermal insulator 22 is interposed between the foot 14 and the outrigger flange 16 to minimize the transfer of heat from the heat sink of the brake disk stack to outrigger flange 16.
Another prior art beam key and wheel assembly is illustrated in FIG. 2 and designated generally by the numeral 28. In this embodiment, the beam key 30 is received upon a foot 32 which is maintained in a channel 34 which is milled from the outrigger flange 36 of the wheel 38. A nut and bolt assembly 40 is again provided for purposes of securing the beam key 30, foot 32, and outrigger flange 36 together. The bolt of the nut and bolt assembly 40 is preferably a shear bolt.
In the beam key and wheel assembly 10 of FIG. 1, the beam key 12 has a rather wide flange to provide a reaction to the overturning moment to which it is subjected in operation. In beam key and wheel assembly 28 of FIG. 2, a similar wide flange is used to react to the overturning moment, but the shear loads are first received by channel 34 milled out of the outrigger flange 36. The prior art structures of FIGS. 1 and 2 are typical in the industry. This embodiment of FIG. 2 allows a smaller diameter bolt to be used than in the embodiment of FIG. 1, since the bolt in the assembly 28 is primarily in tension rather than combined tension and shear. The channel 34 also increases the fixity at the bottom end of the key, reducing the load at the opposite "post" or pinned end of the key. In contradistinction, the assembly 10 has typically required a bushing or sacrificial member in the pinned end of the wheel. This requirement, combined with the necessity of a larger diameter nut and bolt assembly 20 in the embodiment of FIG. 1, can make that embodiment heavier than the embodiment of FIG. 2. However, the precise machining required for the wheels employing the embodiment of FIG. 2 is time consuming and expensive. Specifically, the channel 34 must be milled out using a "stitching" technique, which is both costly and time consuming. The use of right angle milling cutters making passes to machine the slot adds significantly to the cost of manufacturing the preferred prior art embodiment of FIG. 2.
There is a need in the art for a beam key and wheel assembly which provides for the secure and force dissipating engagement between the beam key and the wheel which is attained by employing the technique and structure of FIG. 2, but which enjoys a reduction in both the time and cost to manufacture.